This is something that I've always wanted to experiment with, just have never found the time. AFIK, OpenJPA proper doesn't have support for a shared cache but you could use the OpenJPA TCPRemoteCommitProvider to have distributed cache evictions. This *should* work if you get all of the pieces leaning properly against each other. This method would be quite problematic as you would have to update your p.xm file each time you wanted to add a new cluster member (in addition to managing the ports).
One other option would be to explore using ehcache and openjpa. I can't find a link right now, but hopefully someone can point you in the right direction in the morning. HTH, Rick
